It seems like those controversial stem cells have just added another neat trick to their repertoire: a vaccine made from stem cells protected mice against developing lung cancer under conditions thought to mimic the effects of smoking.

While this sounds like great news to smokers and others who have or are in danger of having lung cancer, Jeffrey Weber, an immunotherapist at the University of Southern California in Los Angeles, advises caution since cancer vaccines made from cells are notoriously more effective in mice than in people.

Lead researcher John Eaton at the University of Louisville in Kentucky also concedes that concerns about testing stem cells on humans means that the vaccine most likely won't be approved for human testing. Despite these restrictions, Weber and Eaton both agree that the finding could lead to breakthroughs in the treatment or prevention of cancer.

In order to test the effects of stem cells on cancer cells, Eaton and his research team injected mice with stem cells and gave the mice a booster shot ten days later. The researchers then transplanted lung cancer cells under the animals' skin — a standard animal model for the disease.

According to their findings, the stem-cell injection protected 20 out of 25 mice from developing tumors while all of the mice that did not receive the vaccine were positive for tumors. Even more effective was a mixture of stem cells and cells engineered to make a molecule that stimulates the immune system. None of the mice given the latter treatment developed tumors when injected with cancer cells.

Eaton is now testing the treatment's effectivity against other types of cancer.